In this work, a computational model of PLLA (Poly L-lactic acid) stent was constructed to study the degradation behavior of the bioabsorbable stent in terms of the loss of mechanical integrity. A degradation model was improved based on experimental data from the literature, as well as a finite element (FE) model was constructed based on the model of the degradation behavior of PLLA material. The results showed that the degradation of the PLLA would switch the material property of stent from a uniform model to a heterogeneous model due to the decline of Young's modulus locally at each location of the stent. Loss of mechanical integrity of the stent showed a bilinear behavior due to the decline of the Young's modulus and the locale failure of the structure, respectively. The breakdown pieces of stent will stay a relative longer time in lesion after the loss of the mechanical integrity of the stent due to the nonlinear response of the degradation degree to the degradation time and strain in the material.